In my home, I have a Wimax ADSL connection. The router connects to the net through a modem (IDU). I just read about dual band routers. It seems to be they are useful when the router is connecting to the net through internet. In my home, only about 1 to 2 devices connect through Wifi. Other devices use cables. So my question is, will it be pointless to have a dual band router in my setup?

The second question is, is there any good tools to test my router. To make sure its working in top shape?

There is a slight chance that if all your devices can use the 5ghz range that you could switch to it to avoid interference in the 2.4 ghz range. Microwaves, portable telephones, other peoples wifi, streaming devices, wireless keyboards and mice are often in the 2.4ghz range. Dual band can help here. You could also get a newer AC router and use both bands at the same time. However most devices only work in the 2.4 ghz range. I dedicate two of my devices in the 5ghz and rest use 2.4 in my house. I do some of my streaming over the 5ghz as it is cleaner and performs better for video streams then the relative dirty 2.4 GHZ

Remember, that is all theroretical, your actual performance and speed may vary as we don't know what other factors may influence the speed.

One last thing to consider depending where you are physically located some Wimax freqs are very close to the 2.4 GHZ and use 2.5 in this case using a 5 GHZ router if all your deviecs can use it could increase not only your internal but reduce interference on the Wimax signal itself. Check wikipedia or your provider to see what freq it uses.

How many wifi networks are in the area? 5ghz is less congested then 2.4. Also dual band routers usually have better cpu's in them so that if you upgrade your internet connection the router will be able to keep up.

1 or 2 devices, not a lot of point for dual band then if you ask me. Do your devices support both 2.4 and 5ghz? If at least one of them does not support 5ghz, then again pointless for dual band.Also keep in mind there are 2 kinds of dual band, ones that can be switched from 2.4 to 5 and others that can do simultaneous both bands.

Essentially my router has two signals per Band at a amplified strength. So yes I found it makes a big difference overall. I easily connect multiple devices at one time and experience no lag or slow down. I only have one device that does 2.4ghz only. I put the others on 5ghz. Any guest that comes over is on the 2.4ghz. Which all of them do 300mb/s anyway. At least my laptops see the two channels and recieve on both at the some time. The USB file sharing is like having another network drive.

To answer the OP's question: YES. Dual Channel makes it better even if your devices are only on 2.4ghz. The added benefit is that later if you get 5ghz capable devices you can have them on that as well and dual channel. The upside of the file sharing can be very helpful.